1. Field of the Invention
This invention relates to the production of integrated circuit devices. More particularly, this invention relates to an integrated circuit structure having a conductive layer which may be placed in betweeen metallization layers to permit subsequent selective removal of the overlying metallization layer, if necessary, for rework.
2. Description of the Prior Art
During construction of an integrated circuit device, it would sometimes be desirable to rework the structure due to some mistake or error in an upper layer. Reworking, rather than scrapping the wafer, would be economically desirable when a number of correctly constructed lower layers have already been applied beneath the problem layer. However, when two or more metallization layers are already present in the structure and the two layers are in electrical contact with one another due to openings or vias which have already been made through intervening layers, selective removal of the upper metal layer, for example, by etching, without damage to the lower metallization layer, can be difficult and complicated.
For example, Cynkar et al U.S. Pat. No. 4,415,606 describes a process for reworking the upper level metal layer by first forming a photoresist mask to mask the vias leading to the lower metal layer followed by etching of the upper metal layer to remove the unmasked portions of the layer including the defects.
When the lower metallization layer is damaged in attempting to remove the upper metallization layer, removal of the intervening oxide layers is necessitated as well. However, since the etchants which would be used to remove intermediate oxides would also remove lower oxide portions in underlying transistor structures formed in the silicon wafer, the wafer, in essence, cannot, in such instances, usually be reworked and must be scrapped.
There, therefore, exists a need for a construction which will permit the necessary electrical connection between two or more metallization layers without interfering or inhibiting the subsequent removal of the outermost of the layers if it later becomes necessary to rework the structure.